Allow a selection of tracks

[Tbaut]

Creating this as I believe it'll be one of the most demanded feature: track selection
Since our delegating system already has the code to handle everything needed to only delegate on the right tracks (per default it's all of them, see getDelegateTx

dashboard/src/pages/Delegate/index.tsx

Line 103 in 692497d

const tx = getDelegateTx({

) all that's missing is a nice UI.

Note: Every track should be selectable, the transaction logic is clever enough already to undelegate/unvote if needed.

I guess we can do a very simple "Advanced" menu in a ContentReveal and show a list of checkboxes with tracks (on 3 or 4 columns?) with their name and number. By default they're all selected.

[Tbaut]

e.g something like this (no need for info tooltip for now)